. . Houston is largely located within the Northern Humid Gulf Coast Prairies level IV ecoregion (34a) a subset of the Western Gulf coastal grasslands level III region as defined by the United States Environmental Protection Agency This region is generally underlaid by Quaternary-aged sand silts and clays (clay clay loam or sandy clay loam) and covered by grasslands with occasional clusters of oak trees.
. . In 1821 the Mexican War for Independence severed the control that Spain had exercised on its North American territories and the new country of Mexico was formed from much of the lands that had comprised New Spain including Spanish Texas the 1824 Constitution of Mexico joined Texas with Coahuila to form the state of Coahuila y Tejas the Congress did allow Texas the option of forming its own state "as soon as it feels capable of doing so.", Texas lies at the juncture of two major cultural spheres of Pre-Columbian North America the Southwestern and the Plains areas the area now covered by Texas was occupied by three major indigenous cultures which had reached their developmental peak before the arrival of European explorers and are known from archaeology These are:.
Knife River Molalla